The Bmi Index...

WilliamG

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We all know how it works. But we all view it differently. Athletes, body builders, weekend warriors...

30 years ago, we all would look it up and say: "One size does not fit all". "What if I work out and some of it's muscle weight"? Then we'd test using some sort of conductivity test. Or even take the plunge in a tank of water to measure our body fat.

Maybe it's not so wrong. Maybe a 6 foot guy with no ass should way less than around 170? Maybe we are trying to cover for being fat? This came to me as I was looking to see where I'm no longer "overweight".
 

Murphys

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We all know how it works. But we all view it differently. Athletes, body builders, weekend warriors...

30 years ago, we all would look it up and say: "One size does not fit all". "What if I work out and some of it's muscle weight"? Then we'd test using some sort of conductivity test. Or even take the plunge in a tank of water to measure our body fat.

Maybe it's not so wrong. Maybe a 6 foot guy with no ass should way less than around 170? Maybe we are trying to cover for being fat? This came to me as I was looking to see where I'm no longer "overweight".
I loathe the BMI. I don’t think it’s accurate. Per the BMI, I’m about 80 lbs over weight, and while I know carry extra weight (and am working hard to lose it), I am not 80 lbs overweight.

I get the need for a quick and easy to determine one’s health based on weight. But I don’t think the BMI is what should be used. But it is. Especially with insurance companies.
 

WilliamG

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I loathe the BMI. I don’t think it’s accurate. Per the BMI, I’m about 80 lbs over weight, and while I know carry extra weight (and am working hard to lose it), I am not 80 lbs overweight.

I get the need for a quick and easy to determine one’s health based on weight. But I don’t think the BMI is what should be used. But it is. Especially with insurance companies.

I fight this too. I'm now finally down to 190 but "should be" 165-170'ish according to this 19th century algorithm. I'm thinking, for those that don't do strength training in the traditional sense. And don't have the muscle mass... It's perhaps not far from the truth.

I mentioned that I have no ass. So using my suggested BMI figure... My current ass makes sense. Add to that I'd have have to do some serious glute work to get an ass to match my current weight. :laughing:
 

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The inventor of BMI has stated that it is only useful for evaluating large populations of people, where some if the individual factors average out, and is useless for evaluating a single individual. Nevertheless, a former employer wanted to charge me thousands of dollars in health insurance surcharge because my BMI was over a threshold. My last employer, before I retired early, still required BMI screenings. The nurse took one look at me, said "You've got a lot of muscle" and proceeded to fudge the number to normal. There should be a class action lawsuit, where any party using BMI to penalize people has every last penny taken from them, because it is fraud. On a scientific basis, the units of BMI (mass per length squared) make no physical sense, providing another indicator that the measurement is a fraud.
 

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My BMI is 29. It says I'm obese.
It's not a very reliable indicator for many people, but if you're just starting your fitness journey is pretty useful.

I recommend you calculate your body fat percentage instead using tape measurements.

Body Fat Calculator

Again, this isn't totally accurate. It has a variance of about ±3.5% but it's still decent, and definitely better than BMI.
 

Juanlw4444

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The BMI was created in the early 19th century by a mathematician. He had no medical training. The subjects used were all male and did not account for differences in gender, body frame, etc. A more accurate measurement would be to measure the percentage of body fat compared to other tissues, or determining the location of body fat which is a better determinant of health outcomes.
 

WilliamG

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The inventor of BMI has stated that it is only useful for evaluating large populations of people, where some if the individual factors average out, and is useless for evaluating a single individual. Nevertheless, a former employer wanted to charge me thousands of dollars in health insurance surcharge because my BMI was over a threshold. My last employer, before I retired early, still required BMI screenings. The nurse took one look at me, said "You've got a lot of muscle" and proceeded to fudge the number to normal. There should be a class action lawsuit, where any party using BMI to penalize people has every last penny taken from them, because it is fraud. On a scientific basis, the units of BMI (mass per length squared) make no physical sense, providing another indicator that the measurement is a fraud.

Well that's an indictment of failure for our current for profit healthcare system... But I digress.

I thought about trying to use BMI as a simple goal. Heck, it won't kill me if I lost weight. But I think about our "natural" health based on normal day to day activities (subtracting serious weight training). I know many are fitness folks with low fat and high muscle percentages. This is not for them. I'm talking Joe Married Guy with three kids who does not go to a gym (on purpose). I'm thinking BMI is not out of spec for what that type of person should weigh right? Less muscle mass (which is heavier than fat) puts one in the realm of the BMI index then.

And that is what sparked my quest. So many answers to being overweight are to build muscle mass to change the proportion. But here's my thing: The heart does not care about the proportion. It cares about the fat content. Am I being to simplistic (having just had a angiogram)?
 
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CaptainRugby

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BMI isn’t great. The main problem is that BMI is a tool, among others, of determining health in relation to weight. It doesn’t work for everyone, particularly those who are put average men. Doctors, the media, and others in the health and fitness industry treat BMI is the litmus test for health, which it certainly isn’t and wasn’t meant to be.
 
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According to BMI I'm borderline overweight. It's not applicable to bodybuilders or people with a lot of muscle, but it's probably applicable for easy, high level weight analysis 80%+ of the population. As @Juanlw4444 said, ideally you could measure body composition but that is a bit more involved and, until recent technological developments, has been difficult to perform accurately (i.e. skin fold measuring).
 

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According to BMI I'm borderline overweight. It's not applicable to bodybuilders or people with a lot of muscle, but it's probably applicable for easy, high level weight analysis 80%+ of the population. As @Juanlw4444 said, ideally you could measure body composition but that is a bit more involved and, until recent technological developments, has been difficult to perform accurately (i.e. skin fold measuring).

Agreed. I put this all in the first post.

What I'm debating is the BMI for "very average" person. Not a gym rat. Makes bad food choices... In this case I believe BMI is not far from reality for these folks. If you don't exercise, then you are prevented from over eating if you want to stay in range. It's not for those with a serious strength training and diet plan.

But what about this..?
Someone who is putting on muscle in the way of body weight IS changing their % of BF. No doubt. But they must also reduce the fat at an equal or better amount to reduce the load on the heart. We all know the "beefy" lifter. I'm not talking about the guy following a planned regime of leaning out. I'm talking about the dad with 3 kids, who still pumps some weight at the gym - but also keeps a big belly. So yes, this "improves his fat percentage - but only adding muscle weight. Does this make sense? And as I said, it would only be accurate in a pool test.
 

Brachy

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Tests can be screening or diagnostic.

Screening tests are used to pick up individuals in a population who MAY have a problem, whereas diagnostic tests are for finding the problem.

BMI is a screening test and is fairly reliable and simple to use.

The problem occurs when a screening test is used for diagnosis so instead of a person “possibly” having a problem, he/she is deemed to an established pathology.
 

Scarletbegonia

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Tests can be screening or diagnostic.

Screening tests are used to pick up individuals in a population who MAY have a problem, whereas diagnostic tests are for finding the problem.

BMI is a screening test and is fairly reliable and simple to use.

The problem occurs when a screening test is used for diagnosis so instead of a person “possibly” having a problem, he/she is deemed to an established pathology.

great first post! And welcome.


everyone:
Here’s a piece (opinion, I gather, but with some history) on the BMI
Racism, western Eurocentrism, insurance companies, and a cameo by Ancel Keys.
The Bizarre and Racist History of the BMI
 
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Juanlw4444

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deleted1074483

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For those saying muscle weighs more than fat, don’t forget a kilo is a kilo, a pound is a pound.

My curiosity is where bone density and bone circumference play in.

BUT muscle is more dense, so 'size for size' a pound of muscle is actually smaller than a pound of fat due to density of muscle.

Which is why a very lean toned person can weigh as much or more than a 'fat' person - the major failing with BMI is that it works on pure weight only not on the type of weight it is (ie muscle or fat).

For an 'average' person though it can be a good indicator of weight gain/loss, or when just comparing with yourself.
 

Scarletbegonia

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BUT muscle is more dense, so 'size for size' a pound of muscle is actually smaller than a pound of fat due to density of muscle.

Which is why a very lean toned person can weigh as much or more than a 'fat' person - the major failing with BMI is that it works on pure weight only not on the type of weight it is (ie muscle or fat).

For an 'average' person though it can be a good indicator of weight gain/loss, or when just comparing with yourself.

Still a person at 150 lbs is the same weight as any other person at 150 lbs, be one pregnant, musclebound or soft. and this is where charts fail.
 
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oldguyontinder

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It’s horrible and encourages eating disorders... my own doctor told me, that while I need to lose weight, to completely ignore BMI. According to the chart a man 6’3” is healthy weighing 160 lbs, which is complete trash. Getting your waist and gut measurements down to healthy numbers is the best way to monitor your body comp without fancy gadgets.
 
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Scarletbegonia

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It’s horrible and encourages eating disorders... my own doctor told me, that while I need to lose weight, to completely ignore BMI. According to the chart a man 6’3” is healthy weighing 160 lbs, which is complete trash. Getting your waist and gut measurements down to healthy numbers is the best way to monitor your body comp without fancy gadgets.
You mention gadgets. on the pro side, a fat percentage scale might be more applicable than charts for many people.